The present invention relates to a semiconductor device and a manufacturing method thereof, and particularly to a solid-state image sensor having a so-called back-side-illumination light receiving element and a manufacturing method thereof.
A solid-state image sensor is a semiconductor device in which an electrode, wiring, and a light receiving element such as a photodiode are formed over the front surface of the semiconductor substrate, and normally has a so-called front-side-illumination structure in which the light receiving element is illuminated with light for photoelectric conversion emitted from thereabove (from above the front surface thereof).
However, the front-side-illumination light receiving element is illuminated with light from above metal wiring formed over the light receiving element. As a result, a part of the light is reflected by the metal wiring and the like, resulting in the problem that the light does not efficiently reach the light receiving element. To solve the problem, a solid-state image sensor having a so-called back-side-illumination structure has been developed in which a light receiving element is illuminated with light for photoelectric conversion emitted from therebelow (from below the back surface thereof). Solid-state image sensors each having a back-side-illumination structure are disclosed in, e.g., Japanese Unexamined Patent Publication No. 2005-150463 (Patent Document 1), Japanese Unexamined Patent Publication No. 2010-212307 (Patent Document 2), Japanese Unexamined Patent Publication No. 2010-147230 (Patent Document 3), Japanese Unexamined Patent Publication No. 2009-252963 (Patent Document 4), and Japanese Unexamined Patent Publication No. 2008-147332 (Patent Document 5).
In a back-side-illumination solid-state image sensor, a light receiving area can be increased compared with that in a front-side-illumination solid-state image sensor. Accordingly, the back-side-illumination solid-state image sensor has the advantage of an improved sensitivity of detecting light received thereby. Therefore, it has been expected to apply a back-side-illumination solid-state image sensor to a high-density and high-sensitivity image sensor or the like.